Are Three Cylinder Engines the New Four?

March 23, 2017 •

2018 Ford Fiesta ST

(Image via Road Show by CNET)

Engines have even numbers of cylinders because it smooths out the vibrations from the suck-squeeze-band-blow four stroke combustion cycle. Just a few vehicles, (the 2.5 liter VW Golf/Rabbit and some Volvos,) were ever sold with five cylinder engines. But engines are getting smaller, in terms of displacement, and now it seems they’re losing cylinders too.

Not so long ago a V6 in the Ford F-150 pickup would have been unthinkable, but today it sells rather well. The same goes for the 2.0 liter, four cylinder in the Mustang. Again, quite the success. But what about three cylinders?

Ford Bringing Three Cylinders

The ST is Ford’s hot version of the subcompact Fiesta. It’s a very quick little car appealing to the driving enthusiast who doesn’t want to spend too much money. Under the hood there’s a 1.6 liter turbocharged four-cylinder making 197 hp and 177 lb-ft of torque. No, those aren’t supercar numbers, but they make the ST quite the pocket rocket.

But in 2018 the ST is changing. The engine shrinks slightly, to 1.5 liters, but it also loses a cylinder. That sounds like a recipe for vibration and anemic performance, but the data says otherwise. With the same horsepower and more torque than before, the three-banger Fiesta promises to be both quicker and more fuel-efficient.

“And what,” you ask, “about vibration?” Well in a clever piece of engineering, Ford is using the rotation of the engine pulley to cancel out the crankshaft imbalance. In addition, there’s a host of technological do-hickeys that feed the air and fuel in, let the exhaust gases out, and make all that power.

Other Three Cylinder Cars

The Fiesta ST won’t be the first three cylinder car on the market. BMW’s Mini’s have used a 1.5 liter three-cylinder since 2014. They handle vibration with a balance shaft that turns in the opposite direction to the engine. And of course, the less entertaining Fiestas have used three-cylinder power for several years.

Downside of Three Cylinders?

Particularly on a car like the ST, how it sounds is important. It’s hard to imagine three cylinders sounding as good as four, let alone six, but Ford say they’ve taken care of it. As three-cylinder engines appear set to proliferate it seems we’ll all have a chance to hear one soon!